In the above context, the public access terminals include telecommunications means for communicating via a telecommunications network providing users with high bit rate access to their mobile gateway from their portable telecommunications object, for example. The high bit rate access is made possible, firstly, by the capacities (from 512 kbits to 1024 kbits) of the access network, which is preferably an asymmetrical digital subscriber line (ADSL) network, and, secondly, by the capacities (700 kbits) of wireless communications links, whether short-range radio links, such as Bluetooth links, or infrared links. Clearly the respective bit rate capacities of the access networks and the wireless links are similar, which guarantees a high information bit rate throughout the communications channel. The portable telecommunications object and the public access terminal must be equipped with respective wireless communications means, of course.
Access by a user to his mobile gateway can be envisaged in the following manner:    1. The user connects to a public access terminal using his mobile telephone and a Bluetooth link, for example. The terminal and the mobile telephone authenticate each other, the mobile telephone being identified by its mobile subscriber ISDN number (MSISDN), and the user of the mobile telephone is himself optionally authenticated.    2. Using the MSISDN of the mobile telephone, a URL server enables the public access terminal to recover the URL of the mobile gateway of the user. The connection is secured by mutual authentication of the terminal and the server and by encryption and/or authentication of messages using an appropriate protocol, such as the SSL v3 protocol.    3. The public access terminal connects to the gateway transparently by sending it a signed token certifying the identity of the mobile telephone, such as its MSISDN or some other identifier. The SSL v3 protocol enables the public access terminal and the mobile gateway to authenticate each other and where applicable to assure the confidentiality and/or the integrity of information exchanged. The terminal therefore behaves like a trusted third party with respect to the gateway, by guaranteeing authentication of the mobile telephone. If the user is authenticated via the mobile telephone, the telephone then serves as a trusted third party in relation to the terminal and the gateway.    4. When the above steps have been completed, the mobile telephone, and where applicable its user, have been identified to the gateway. The public access terminal then serves as a relay for the users and their gateway: it sends requests to the gateway and returns results to the users.
The question that arises in the above access procedure is whether the public access terminal can authenticate the mobile telephone by means of a Bluetooth wireless call, as in step 1 above.
Although Bluetooth security services, for example, enable secure connections to be set up between a plurality of personal units, the units need to share secret information such as a personal identification number (PIN) in order to be able to do this. The Bluetooth security protocol is therefore insufficient on its own to achieve secure connection of a plurality of users and a public unit. This is because Bluetooth security is designed to cover private usage in which only a few units with a Bluetooth interface can communicate with one another and authenticate one another using secret information that they share. The secret information is the key security factor.
It follows that the recommended implementation of Bluetooth security is not applicable in the context of the invention, as it presupposes a private environment, whereas the authentication of a public access terminal and at least one mobile telephone required in the context of the invention has to be effected in a public environment. Merely sharing secret information is not sufficient to guarantee authentication by the terminal of the individual mobile telephones, since each mobile telephone must have its own secret information, and each public terminal must know that secret information.